The present invention relates to liquid antisettling compositions that provide excellent pigment suspension properties to organic compositions and effective sag control to organic coating compositions.
It is known in the art to add pigment suspension or antisettling agents to organic coating compositions to prevent pigments or other finely divided solid particles from settling during storage. It is also known to add these agents to organic coating compositions as rheology modifiers to prevent sagging when the coating composition is applied to a vertical surface. The art has constantly sought materials that are useful to control the pigment suspension properties of various organic compositions, provide effective sag control and, additionally, are easy to use.
U.S. Pat. No. 3,123,488 discloses a heat-stable composition useful to modify the rheological and suspension properties of non-aqueous fluid systems containing finely divided solid particles. The composition disclosed therein consists of a finely divided polyethylene wax dispersed in an organic liquid vehicle that is compatible with paint. The composition is water free and the organic vehicle is present in an amount of from 40% to 95% by weight based on the weight of the total composition. The emulsifiable polyethylene wax has a melting point between about 208.degree. F. and about 221.degree. F., a penetration hardness between about 1 and about 6, an acid number between about 2 and about 50, and a saponification number between about 9 and about 25.
U.S. Pat. No. 3,184,323 discloses a heat stable composition that is useful to modify rheological and suspension properties of non-aqueous fluid systems containing finely divided solid particles. The composition consists of a finely divided polyethylene wax dispersed in an organic liquid vehicle which is compatible with paint. The composition is described as water free and the organic vehicle is present in an amount of from about 40% to about 95% by weight based on the weight of the total composition. The emulsifiable polyethylene wax has a melting point between about 200.degree. F. and about 230.degree. F., a penetration hardness between about 1 and about 10, an acid number between about 0 and about 5, and a saponification number between about 9 and about 25. The emulsifiable polyethylene waxes differ from those disclosed in U.S. Pat. No. 3,123,488 in that the free acid groups contained in the emulsifiable polyethylene wax are reacted with chemicals such as ethylene diamine, monoethanolamine, toluene diisocyanate, and sodium hydroxide to achieve a lower acid number.
U.S. Pat. No. 3,562,194 discloses an additive for preparing thixotropic oil-based paints. The additive is a salt of a reaction product of a polyvalent inorganic acid such as sulfuric, phosphoric, or boric acid and an ester such as an ester of low epoxide oxygen content of an unsaturated aliphatic carboxylic fatty acid and a saturated alcohol, or an ester of low epoxide content of an unsaturated fatty alcohol and carboxylic acid. This patent describes the use of sulfated/sulfonated castor oil as a rheology modifier and a suspending agent for pigments in oil-based paints.
U.S. Pat. No. 3,937,678 discloses a process for improving the rheological properties and suspension properties of non-aqueous fluid systems containing finely divided solid particles by adding to the non-aqueous fluid system a mixture of an amide wax having a melting point of from about 100.degree. C. to about 160.degree. C. obtained by reacting a hydrogenated castor oil fatty acid or an organic acid mixture containing at least 30 molar percent of hydrogenated castor oil fatty acid with amines, and an emulsifiable polyethylene wax having an acid number of from about 2 to about 50, a softening point of from about 95.degree. C. to about 120.degree. C., a density of from about 0.92 to about 0.98, and a penetration hardness of from about 1 to about 20.
U.S. Pat. No. 3,985,568 discloses a creamy paste comprising finely divided particles of an emulsifiable polyethylene wax suspended in a sulfated/sulfonated castor oil solution. The paste contains from 1 to 6 parts emulsifiable polyethylene wax per part of sulfated/sulfonated castor oil. The composition is useful for modifying the rheological and suspension properties of non-aqueous fluid systems containing finely divided solid particles.
Japan Kokai 76 04 087 discloses the use of emulsifiable polyethylene waxes to stabilize a dispersion of pigments in water thinned coating compositions.
Most antisettling agents and rheology modifiers of the art that are based on emulsifiable polyethylene waxes dispersed in an organic solvent are creamy or hard pastes. These compositions are difficult to handle during the manufacture of paints. To avoid the use of a gel, a paint manufacturer would have to dilute the creamy paste or gel with a solvent to prepare a pourable or pumpable fluid product. However, this procedure is undesirable due to the necessity of high shear mixing equipment to achieve homogenous dilutions. Further, a separate mixing tank is also required.
Despite the numerous types of pigment suspending agents known in the art, new additives for modifying the rheological and suspension properties of non-aqueous fluid systems containing finely divided solid particles are desired that are efficient and can be easily handled.